The Mucus Core will perform key mucin biochemical and biophysical measurements for all the Projects of the tPPG, which as a group are devoted to developing effective treatments to enhance mucus clearance based on a solid understanding of the physical and biochemical forces and factors which affect mucus viscoelasticity, transport, and the adhesion of mucus to epithelial surfaces. Emerging data from the Sheehan/Kesimer laboratory indicate strongly that proteins associating tightly with mucins are essential to mucus viscoelasticity and participate in airways defense. For Projects II and III, accordingly, the Core will use mass spectrometry approaches to identify the proteins that associate intimately with mucins, the mucin-interacting proteome. The Mucus Core will offer the following services to the Projects: 1. Mucin concentrations in mucus or sputum samples submitted by all the Projects will be determined and the mucins identified. Complementary biophysical and biochemical quantitative techniques will be used for samples containing quantities of mucin in the ?g, sub-?g, and ng ranges, as specified below. Mucins will be identified by ELISA and/or agarose gel electrophoresis (aGE)/Western blotting. 2. Mucus rheology, i.e., its viscoelastic properties, will be determined for ]x\ sized samples sputum samples from Project III using a cone and plate rheometer. 3. The proteins comprising the mucin-interacting proteome will be identified by mass spectrometry for all three Projects, and the results from human vs. mouse and the different treatments analyzed differentially. 4. The effects of N-acetyl cysteine, and other reducing agents used in all the Projects will be determined for mucus rheology and mucin biochemistry. 5- Core C will provide purified mucin standards for testing the mucus reducing agents. 6- Measurement of mucus partial osmotic pressure.